Atom Economical Polycondensation.

Chlorine, an atom economical auxiliary for asymmetric aldol reactions.

An auxiliary strategy has been developed for asymmetric reactions of aldehydes in which the auxiliary itself is not chiral, but a single chlorine atom introduced via organocatalytic α-chlorination. The stereodirecting influence of the chlorine atom is then exploited prior to its removal by radical reduction. This strategy is demonstrated in the synthesis of several aldols (92-99% ee) and the na...

Atom-Economical Palladium Carbon-Catalyzed de Novo Synthesis of Trisubstituted Nicotinonitriles.

A de novo palladium carbon-catalyzed synthesis of trisubstituted nicotinonitriles from easily synthesized homopropagylic or homoallylic aromatic alcohols in the presence of nitriles has been explored. The mechanism proceeds with an interesting generation of a Pd(II)-C palladacycle followed by an oxidative aromatization to generate the pyridine core. The pyridine core is generated with a notewor...

Nickel (0) Catalyzed Kumada Chain Transfer Polycondensation

Fast screening of polycondensation catalyst, Determination of the kinetic data of catalyzed polycondensation in polyethylene terephthalate synthesis

Differential scanning calorimetry (DSC) belongs to the family of thermal analysis methods. In general thermal analysis is the determination of substance properties in dependence on temperature. Thermodynamic data (heat capacity, phase transition, enthalpy) and kinetic data can be determined by methods of thermal analysis. The greatest advantage of thermal analysis is the easy handling and the o...

Economical Numbers

A number n is said to be economical if the prime power factori-sation of n can be written with no more digits than n itself. We show that under a plausible hypothesis, related to the twin prime conjecture, there are arbitrarily long sequences of consecutive economial numbers, and exhibit such a sequence of length 9.